Feature: Introduce Super Admins (#705)

* Feature: Introduce Super Admins

- added new devise model for super user
- added administrate gem
- sample dashboards for users and accounts

Co-authored-by: Pranav Raj Sreepuram <pranavrajs@gmail.com>

app/controllers/super_admin/devise/sessions_controller.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+class SuperAdmin::Devise::SessionsController < Devise::SessionsController
+  def new
+    self.resource = resource_class.new(sign_in_params)
+  end
+
+  def create
+    return unless valid_credentials?
+
+    sign_in(@super_admin, scope: :super_admin)
+    flash.discard
+    redirect_to super_admin_users_path
+  end
+
+  def destroy
+    sign_out
+    flash.discard
+    redirect_to '/'
+  end
+
+  private
+
+  def valid_credentials?
+    @super_admin = SuperAdmin.find_by!(email: params[:super_admin][:email])
+    @super_admin.valid_password?(params[:super_admin][:password])
+  end
+end